<style>
span {
    font-weight: bold;
    color: yellow;
    border: 5px solid red;
    display: none;
}

.all {
    all: unset;
}

.unset {
    font-weight: unset;
    color: unset;
    border: unset;
    display: unset;
}
</style>
<body>
  <span class="all">all</span><br>
  <div style="color: green; font-weight: normal;">
    <span class="unset">unset</span>
  </span>
</body>
